[MRCA] Fast RTTY

[W2HX]

Hi Ray. I would venture to guess that 100 wpm is not exceedingly common. I have a M28KSR that has the gear shift and I am sure others do too. But it is less common. While I DEFINITELY applaud you for wanting to use rudimentary (by today's standards) technology for this project, that speed conversion issue might just be what would tip me over to an arduino or something. I also wonder whether you could change the baud rate on the UART within the MX terminal? The chip may be able to be re-wired for that speed. Alternatively, you could potentially replace the crystal that operates the uart with an Epson oscillator thingy with a frequency that corresponds 45.45 baud (from 75 baud). Just some thoughts. Good luck!
73 Eugene W2HX


From: MMRCG at groups.io <MMRCG at groups.io> On Behalf Of Ray Fantini
Sent: Friday, February 12, 2021 3:25 PM
To: 'MRCA' <mrca at mailman.qth.net>; MMRCG at groups.io
Subject: [MMRCG] Fast RTTY

Plowing forward on my 1980 digital RTTY project, going to be building the input UART that will convert the digital level output of the Dovetron TU this weekend. That will provide me with a five bit word that the ROM board will convert to a seven bit ASCII word that the MX Tactical terminal will understand.
The MX family of terminals run at 75, 600 and 2400 baud. I have the UART that converts the seven bit word to a serial word the MX understands and sends it to the MX at a blinding high speed rate of 75 baud. The real problem will be going from the MX to the Dovetron at 60 WPM, going from 60 WPM (45.5 baud) up to 100 WPM (75 baud) is no issue. The problem occurs with the way the MX Terminal works. You cannot transmit in real time. You have to write to a buffer in the terminal and then go to the SEND function on the terminal and dump the entire message at once. When going from 75 baud to 45.5 baud you would have to store data in the message to make up for the added time required to clear the data thru the UART.
Long story short, wont have any issues reading 60 WPM traffic on the terminal but looks like I can only transmit if both stations are running at 100 WPM
What's the feeling about getting some of the 28 people out there to get those old teleprinters to chug along at that speed?

Ray F/KA3EKH

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